From the release notes:
Fixed an issue with some XML-RPC processors and the client library that requires that the request be typed text/xml. It was previously being typed the default by Net::HTTP which is "application/x-www-form-urlencoded".

Also added debugging features. Set #debug = true on any of the XML::XMLRPC::* classes to get output -- setting it on the client will set it on both the builder and parser classes to get output of the full transaction.